Here is a HoverBorderLayout I made. It is compatible with GXT 2.2.4. It expands the popup of a collapsed panel on mouse over and collapses it on mouse out. You can set the width of the collapsed section (standard is 24, min is 2).

Hi Carl ,
First of all, thank you for this component, it's what I'm looking.

Here is an experience sharing,
I found if BorderLayoutData is set with a ratio size (size is small than 0),
the HoverBorderLayout won't work normally caused by the popup.el always get 0 as it's width, then the checking in mouse over is wrong.

I just replaced ration size with a fixed width, then it works perfectly.

I hadn't tried with percentage widths before. Next time I'm working on it I'll take a look.

I'm trying to get the hover to work properly on IE8 but there appears to be a border around the page that means the mouse over is very hard to trigger. IE6 and IE9 are fine (no browser border around the page)